Demounting machines have been long known and widely used to demount and mount vehicle wheel tires from and to their rims.
Such prior art demounting machines comprise a base which has a rotating platform arranged thereon for receiving the wheels in a lying position, and is equipped with lock devices, designed to grip and hold the wheel rims during the work operations.
A generally vertical column extends upwards from the base, and supports a substantially horizontal arm at its upper end, which arm is typically mounted to a carriage which slides along the column.
A rod facing towards the platform, i.e. downwards, is mounted to a free end of this horizontal arm, and is in turn able to slide relative to the arm, towards or away from the platform.
This rod has a connector at its bottom end, for mounting work-tools thereto, which tools are interchangeable as needed.
A second column is provided parallel to the column, and is also generally linked to the base, and has a de-beading device supported thereon, i.e. a device designed to press the tire bead either to remove it from the edge of the rim to which it is mounted or to push the bead into the inner channel of the rim.
This de-beading device is composed of two substantially horizontal and parallel arms, which are mounted, overhanging towards the rotating platform, on independently sliding carriages, which slide along guides formed on such second column, and are designed to move towards or away from and parallel to each other, and are driven by specially designed fluid dynamic units.
Each arm of the de-beading device has a bead pressing tool at its free end, which tool is typically a frustoconical element, freely rotating with an appropriately tilted axis of rotation, for its outer edge to act upon the tire bead of a wheel, when the latter is locked on the work platform, and to press it, as mentioned above, into the channel of the rim to which it is mounted, or out of such channel.
A tire mounting/dismounting machine is known from European patent EP 1946946.
According to the above patent, the tire mounting/dismounting machine comprises a base, rotating means for supporting and blocking a wheel and a column associated to the base.
A first arm and a second arm are slidably mounted on the column and an upper first debeader tool and a lower second debeader tool are mounted respectively at the free ends of each arm.
At the free end of the first arm a head is mounted, being rotatable with respect of an axis, and from said head a mounting tool, a dismounting tool and a first debeading tool project.
The tools are mounted in reciprocal positions such that do not interfere with one another and such that by rotating the head with respect to the first arm a same position can be reached for each of the tools.
The head is provided with blocking means for blocking the former in three different positions, a same work position for each of the tools corresponding to each of the three different positions.
A machine for fitting and removing tires and wheel rims for vehicles is known from the European patent EP 1475252.
According to this patent the machine comprises a frame for supporting elements for coupling and turning a rim onto.
A working assembly is supported movably by the frame and comprises a working head for fitting and removing the rim/tire associated with a first translational actuation, and is provided with a tubular pusher transverse to the rotation axis.
The working assembly is associated with an abutment surface associable with a tire side and with at least one tire removal tool associated with a second actuation for alternate movement between an inactive configuration at least partially within the pusher, and at least one active configuration protruding at least partially from the pusher.
A machine for fitting and removing tires and wheel rims for vehicles is known from European patent EP 1897708.
According with said patent, the machine comprises a supporting structure of clamping and rotating means, for clamping and rotating the rim of a vehicle wheel around a rotation axis, at least one operating unit which is associated moving with the supporting structure and which comprises an operating head for fitting and removing a tire onto/from the rim provided with a pushing body for pushing at least one portion of the side surface of the tire and with a grip tool gripping at least one section of the tire bead.
The operating unit further comprises an actuator element for operating the sideways movement of the operating head with respect to the structure and guide means of such sideways movement along a substantially curvilinear direction between a first configuration in which the operating head is substantially close to the clamping and rotation means and a second configuration in which the operating head is substantially moved away from the clamping and rotating means.
While these tire demounting machines have a substantially adequate operation, they still suffer from certain drawbacks.
A first drawback is that they have a very complex and bulky structure, as they have to be equipped with two or even more columns extending from the base, which are required for supporting the various work-tools.
A further drawback is that the distance between the columns in the work position and the rotating platform and hence the overall length of the tire demounting machine is considerable and further increases when of the columns is able to be displaced towards the rear portion of the tire demounting machine, away from the rotating platform, to clear the work space therearound.
An additional drawback is that the distances of the columns from the rotating platform must be adjusted at each processing step, for proper placement of the work-tools relative to the wheels lying on the rotating platform.
Another drawback is that the heights of the work-tool supporting columns should allow the tire repairer to lift the tools from the work space and lie and remove the wheels on and from the rotating platform, without interfering with the tools thereabove.
Also the second column is generally equipped with a joint for articulation relative to the base, which allows it to rotate about a vertical axis, thereby moving the arms of the de-beading device away from the rotating platform.
Nevertheless, such joints add complexity and costs to the tire demounting machines that feature them as compared with the demounting machines with fixed columns, and further require an adequate size increase to prevent the structure from being weakened, to withstand the stresses acting upon the joints during operation.
A further drawback is that these tire demounting machines have very high costs due to their complex construction as described hereinbefore.
A further drawback is that not more than two work-tools at a time can be mounted to the connector of the rod supported to the horizontal arm, both arranged on a common support with a joint that, once it is mounted to the connector of the rod, allows rotation about an axis to orient either tool towards the rotating platform.
Therefore, during the various work steps, tire repairers are required to often replace the tools mounted to the connector of this rod, to complete all the required operations on tires.
These replacements, which occur frequently for each vehicle lead to the buildup of a considerable dead time during each working day.